don't return uninitialized memory from bdiff.blocks()
bdiff.blocks() returns a dummy match at the end of both files; the
length of that chunk is never set, so it will sometimes contain random
heap garbage. There are apparently workarounds for this elsewhere:
# bdiff sometimes gives huge matches past eof, this check eats them,
#!/bin/sh
echo 'syntax error' > badext.py
abspath=`pwd`/badext.py
echo '[extensions]' >> $HGRCPATH
echo "badext = $abspath" >> $HGRCPATH
hg -q help help